Report of the Mitigation Session

Macrander, M.1*, Morse, L.2*, Reesor, C.3, Mendes, S.4, Sanders, M.5, Schuster, M.6, Findlay, C.7, Matthews, M. N.8, Southall, B.9

1      Integral Consulting Company
2      Integrity
3      Defence Research and Development, Canada
4      JNCC
5      Transport Canada
6      DW-ShipConsult
7      Aarhus University
8      JASCO Applied Sciences
9      Southall Environmental Associates, USA

* Session Chairs and Corresponding Authors; E-mail: Bruce Martin ( & Michael Macrander (

This report can be referenced as: Macrander, M., Morese, L., Craig, R., Mendes, S., Sanders, M., Schuster, M., Findlay, C., Matthews, M.N., and Southall, B. (2023). Report of the Mitigation Session, OCEANOISE2023, Vilanova i la Geltrú, Barcelona, Spain, 22-26 May. Retrieved from





Key Points

Michael Macrander

Integral Consulting Company

Mitigation Measures as Means to Minimize the Effects of Ocean Noise: Considering the Full Range of Options

– At a high level, mitigation has based on a prioritized triangle of Avoid-Mitigate-Restore
– We need to make sure that the cost and effectiveness of mitigations are balanced.
– We need to consider how to add Restore to the discussion of underwater noise.

Laura Morse


Mitigation and Monitoring for Offshore Wind: Industry Perspectives

– Reviewed requirements for monitoring and mitigation at a high level for upcoming US East Coast wind installations.
– Meeting mitigation requirements can put demands on projects that can extend their duration and /or require more vessels at sea.
– Data requirements to do a better job: effectiveness of NAS, behavioural reactions from tags, hearing recovery.

Craig Reesor

Defence Research and Development, Canada

Marine Mammal Risk Mitigation Strategies for the Canadian Armed Forces

– Provided a summary of efforts to develop a risk-mitigation system for active sonar exercises.
– Combines propagation, animal density, animat modelling, and dynamic regulatory risk layers
– Moving mitigation from an operator-only activity to a pre-exercise risk analysis that lessens the burden on operators during exercises

Sonia Mendes


Managing noise in a marine mammal protected area using area-time limits

– Described the implementation of noise management guidance via the UK Marine Noise Registry, which will have new functions for assessing and managing cumulative noise disturbance in UK special areas of conservation for harbour porpoise.
– No more than 20% of area on a given day. No more than 10% of the area over the season.

Michelle Sanders

Transport Canada

Advancing vessel technologies to contribute to a quieter marine soundscape

– Overview of Canada’s Quiet Vessel Initiative that is researching how to use technological and operational advances to reduce vessel noise.
– Types of projects: lit review, computational design, full-scale tests.
– Project themes: Vessel Design, Cavitation Monitoring, Operational Measures

Max Schuster


Cavitation Inception Speed of merchant ships: analysis and discussion based on data collected in the ECHO program

– Reported on a QVI project to look at CIS since it is the lower limit of usefulness for operational speed reductions to lower noise emissions
– Analyzed ships with at least 100 vessel measurements in the ECHO database.
– There is a wide variance in CIS
– 10 – 12 knots appears to be the point of CIS for most ships.
– High frequency noise comes down faster than low frequency

Charlotte Findlay

Aarhus University

Small reductions in cargo vessel speed dramatically reduce noise impacts to marine wildlife

– Used the J-E model to show speed reductions offer substantial decreases in vessel noise.
– Reductions in level, but also in exposure times
– Few situations where it won’t be effective.

Marie Noel Matthews

JASCO Applied Sciences

Vessel Noise Mitigation: A Focus On Achievable Noise Reduction

– Used modelling and measurements to look at the options for lowering total noise exposures.
– Moving shipping lanes can allow sensitive areas to have reduced noise at the trade off of increased levels in other areas.
– Convoying ships is helpful, particularly in areas with limited numbers of vessel passages

Brandon Southall

Southall Environmental Associates

Strategic approaches to mitigation: Cross-sectoral partnerships to address priority issues

– Things we should do better: let go of older, precautionary approaches that no longer serve conservation. Leverage the knowledge and approaches used by multiple countries, not just one. Allow mitigations to adapt to the big picture so that they are not limited by mandates aimed at rare events prevent doing the right thing in the big picture.
– Things we doing well: Adapting and learning to use new mitigation approaches; Using multi-disciplinary systems approaches; having open and honest discussions about real issues